Procedures exist for replacing diseased intervertebral disks in which the disk material is typically removed from between adjacent vertebral bodies, and the adjacent bodies are fused. This has been done with a cage filled with bone or bone forming proteins placed in between the bodies to fix them to each other, generally to support and promote fusion between the adjacent vertebrae.
In arthroplastic procedures, a pivotally articulated prosthesis is implanted between the vertebrae in the site of the diskectomy. For example, U.S. Pat. Nos. 5,425,773 and 6,063,121 disclose intervertebral arthroplasty devices that use different ball and socket arrangements to permit movement between the vertebrae. The ball and socket is disposed at center between surfaces of plates that are placed against the vertebrae. The intervertebral disk prosthesis disclosed in U.S. Pat. No. 5,556,431 has a core and endplates with a spherical articular surface. The core has an edge rim that limits the range of movement.
Other teachings also provide for translational movement between the vertebrae. U.S. Pat. No. 6,113,637, for instance, shows an intervertebral joint with a ball component engaged with a vertebra and with a trough component, which is engaged with another vertebra. The trough component has a flat portion that allows translation of the ball component on one axes. A prosthesis disclosed in Patent Application Publication U.S. 2002/0128715 shows a flexible central body between two rigid opposing shells to allow combined translation and bending.
There is a need for an improved disk prosthesis that provides improved articulation between the vertebrae between which it is implanted.